JPH05293908A - Production of fiber reinforced thermoplastic resin pipe - Google Patents

Abstract

PURPOSE:To efficiently produce a fiber reinforced thermoplastic resin pipe from the prepreg of thermoplastic resin whose softening point or melting point is regulated to the range of specified temperature. CONSTITUTION:A method for producing a fiber reinforced thermoplastic resin pipe is constituted as follows. Prepreg is constituted of a matrix formed of thermoplastic resin whose softening point or melting point is regulated to 160-300 deg.C and contains reinforcing fiber. The prepreg is interposed between a heat expansional core formed of polyethylene having ultra-high molecular weight and an external mold arranged in the outside of the core. Then the prepreg and the core are heated to soften or melt thermoplastic resin and also to expand the core. Thereafter the core and prepreg are cooled.

Description

Detailed Description of the Invention

[0001]

The present invention has a softening point or a melting point.
The present invention relates to an advantageous method for producing a fiber-reinforced thermoplastic pipe made of a thermoplastic resin at 160 ° C to 300 ° C.

[0002]

2. Description of the Related Art Generally, a continuous fiber reinforced composite material (prepreg) having a thermoplastic resin as a matrix is superior in toughness, heat resistance and environment resistance to a composite material having a thermosetting resin such as an epoxy resin as a matrix. And is remarkably excellent. For this reason, in recent years, fiber-reinforced thermoplastic resin pipes have been made with prepregs that use a thermoplastic resin as a matrix, and these pipes are used as structural members of bicycle structural members, sports / leisure fields such as golf shafts and fishing rods, and aerospace fields. Attempts have been made to use it.

Conventionally, this fiber-reinforced thermoplastic resin pipe is produced, for example, by a so-called internal pressure molding method.
In the internal pressure molding method, a sheet-shaped prepreg is spirally wound to form a cylindrical preform, which is then inserted into a cylindrical outer die, and then the hollow portion of the preform is filled with a heat-expandable rod-shaped medium. After inserting the core, the preform and the core are heated to a temperature equal to or higher than the plasticizing temperature of the thermoplastic resin forming the preform to thermally expand the core in the hollow portion of the preform to soften the thermoplastic resin or The preform is clamped by the pressing force caused by the thermal expansion of the core while melting, and then the preform and the core are cooled together with the cylindrical outer mold, and the core is pulled out from the hollow part of the preform and the cylindrical outer mold is formed. It is a molding method comprising obtaining a pipe by removing it.

In this internal pressure molding method, in the case of so-called super engineering plastics in which the matrix resin of the prepreg is typified by polyether ether ketone (PEEK) having a molding temperature of over 300 ° C., a large temperature above 300 ° C. Thermally expanding polytetrafluoroethylene (PT
Fluorine-based resin mandrels such as FE and Teflon (trade name) are used as heat-expandable cores. Further, when the matrix resin of the prepreg is a thermoplastic resin having a molding temperature of less than 200 ° C., a stretchable rubber tube is used as a core, and hot water or the like is press-fitted therein for heating.
However, if the matrix resin of the prepreg is a thermoplastic resin having a softening point or melting point of 160 ° C to 300 ° C,
The internal pressure molding method could not be satisfactorily performed because there is no suitable core that greatly expands thermally at a temperature of 0 ° C to 300 ° C.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for efficiently producing a fiber-reinforced thermoplastic resin pipe from a prepreg of a thermoplastic resin having a softening point or melting point of 160 ° C. to 300 ° C. To do.

[0006]

The method for producing a fiber reinforced thermoplastic resin pipe according to the present invention has a softening point or a melting point of 160.
A prepreg containing a thermoplastic resin of ℃ ~ 300 ℃ as a matrix and containing reinforcing fibers is interposed between a heat-expandable core made of ultra-high molecular weight polyethylene and an outer mold arranged outside the core. Next, after heating the prepreg and the core to soften or melt the thermoplastic resin and expand the core, the core and the prepreg are cooled.

As described above, according to the present invention, since the heat-expandable core made of ultra-high molecular weight polyethylene is used, the core has a large thermal expansion at a temperature of around 150 ° C. to 300 ° C. Alternatively, it becomes possible to efficiently produce a fiber-reinforced thermoplastic resin pipe from a prepreg of a thermoplastic resin having a melting point of 160 ° C to 300 ° C. Hereinafter, the configuration of the present invention will be described in detail.

The softening point or melting point used in the present invention is 16
A prepreg containing a thermoplastic resin of 0 ° C to 300 ° C as a matrix and containing reinforcing fibers is specifically a matrix of fiber bundles generally called tow in which a plurality of continuous fibers are aligned and arranged in a band in one direction. Impregnated with a thermoplastic resin having a softening point or melting point of 160 ° C to 300 ° C
(One-way aligned prepreg (UD prepreg)) etc. Not only does it have no tackiness or plasticity at room temperature, but it also has high rigidity. It has a sheet or strip shape (slit tape). The reinforcing fiber used for the fiber bundle constituting this prepreg is, for example, carbon fiber, glass fiber, aramid fiber (aromatic polyamide fiber), silicon carbide fiber, boron fiber, alumina fiber or the like having heat resistance and high strength. It is a continuous fiber.

The softening point or melting point is 160 ° C to 300 ° C.
The thermoplastic resin of the matrix, that is, the melting point for the crystalline resin, the softening point for the amorphous resin is 160 ℃ ~ 300 ℃ for the matrix thermoplastic resin, for example, polycarbonate (PC), polyamide (PA), They are so-called engineering plastics such as polypropylene (PP), polyester (PE), and polymer alloys of these.

The heat-expandable core of the present invention may be in the form of a solid mandrel or a hollow mandrel. The ultra high molecular weight polyethylene that constitutes this core is
It has a melting point in the range of 150 ° C ± 20 ° C, and has a molecular weight and molecular weight distribution sufficient to exhibit non-fluidity at temperatures in the vicinity of 200 ° C to 300 ° C. The molecular weight is 1 million or more, preferably 2.5 million. That is all. Those having a molecular weight of about 2.5 million are preferable because they can be easily extruded into a mandrel shape.

In this ultra high molecular weight polyethylene, the diameter is 1
Figure 1 shows the relationship between temperature and radial thermal expansion for a solid mandrel of 4.2 mm ultra high molecular weight polyethylene.
As can be seen from the figure, 8-10 at a temperature around 150 ℃ -300 ℃.
% Thermal expansion (coefficient of linear expansion) occurs. That is, from FIG. 1, ultrahigh molecular weight polyethylene shows a rapid thermal expansion at about 150 ° C. and expands to about 300 ° C. for a total of about 10 ° C.
You can see that it grows by%.

The heating temperature at the time of molding is 30 ° C. to 50 ° C. higher than the softening point or melting point of the thermoplastic resin of the matrix.
It is best to set it to a high temperature, with a softening point or melting point of 160 ° C.
20 when using a thermoplastic resin at ~ 300 ° C as the matrix
It is recommended to set the temperature between 0 ° C and 330 ° C. In the present invention, the core is composed of this ultra high molecular weight polyethylene, but when the core is made of only ultra high molecular weight polyethylene, that is, when the core is a mandrel of ultra high molecular weight polyethylene, it is in use. In some cases, the end of the metal may be oxidized and deteriorated. In particular, thermal decomposition accompanied by oxidation occurs in an air atmosphere near 300 ° C, so that the exposed portion of the end of the core burns black after use. Therefore, when a mandrel of ultra-high molecular weight polyethylene is used as a core, after the use, a regeneration treatment is carried out if necessary. In this regeneration treatment, when thermal decomposition occurs at the end, the end is cut off, and when the end is oxidized and deteriorated, for example, the mandrel is heated at 250 ° C to 300 ° C under a nitrogen gas atmosphere.
Hold in an oven at 0 ° C for virtually no load for 30-120 minutes (until a uniform temperature is reached), then -2 ° C
It may be carried out by gradually cooling at a cooling rate of -10 ° C / min.

In order to avoid such a regeneration treatment, a mandrel of ultra-high molecular weight polyethylene having a fluororesin layer on its surface may be used as a core. Due to the presence of the fluorine-based resin layer, the contact with oxygen is cut off, so that the oxidation of the ultra high molecular weight polyethylene can be prevented. The fluororesin layer may be provided on the surface by covering the mandrel of ultrahigh molecular weight polyethylene with a fluororesin tube. Examples of the fluorine-based resin in this case include PTFE and polyfluorinated alkoxyethylene resin.
(PFA), Fluorinated ethylene propylene ether copolymer resin
(FEP) or the like is used.

The fiber-reinforced thermoplastic resin pipe is manufactured by an internal pressure molding method. That is, first, a prepreg containing a thermoplastic resin having a softening point or a melting point of 160 ° C. to 300 ° C. as a matrix and containing reinforcing fibers was formed into a cylindrical outer mold 1 as shown in FIG. Load it. In this case, a cylindrical preform braided with strip-shaped prepregs may be inserted into the cylindrical outer mold 1.
Alternatively, a sheet-shaped prepreg may be spirally wound to form a cylindrical preform, which may be inserted into the cylindrical outer mold 1. The cylindrical outer mold 1 has excellent heat resistance capable of withstanding the processing temperature at the time of molding, and is, for example, a metal pipe such as a copper pipe.

Next, as shown in FIG. 3, the preform 2
A heat-expandable rod-shaped core 3 made of ultra-high molecular weight polyethylene is inserted into the hollow part of FIG. In this way, a prepreg containing a thermoplastic resin having a softening point or melting point of 160 ° C. to 300 ° C. as a matrix and containing reinforcing fibers is provided with a heat-expandable core 3 and a cylinder arranged outside the core 3. It is interposed between the outer mold 1.

Then, the preform 2 and the core 3 are heated to thermally expand the core 3 in the hollow portion of the preform 2 to soften or melt the thermoplastic resin and to press the core 3 by thermal expansion. Clamp the preform 2. The heating in this case is performed, for example, by putting the whole into a heating furnace. After that, the preform 2 and the core 3 are cooled together with the cylindrical outer mold 1, and the core 3 is preformed with the preform 2.
The pipe 4 as shown in FIG. 4 can be obtained by pulling it out from the hollow part and removing the cylindrical outer mold 1.

[0017]

【Example】

Example 1 UD prepreg sheet reinforced with unidirectional carbon fibers using polycarbonate as a matrix (prototype prepreg manufactured by Mitsui Toatsu Chemicals, Inc., finished thickness 150 μm / ply, thickness in prepreg state is about 250 μm / ply)
Was used to form a pipe having a diameter of 24 mm and having a laminated structure of [± 30 °] ₃ by an internal pressure forming method.

The outer mold was a copper pipe having an inner diameter of 24 mmφ, and the core was a round bar made of ultra-high molecular weight polyethylene having a diameter of 20 mmφ. As molding conditions, it was kept in an oven at 280 ° C. for 1 hour and then rapidly cooled in cold water. The pipe molded in this way has no externally visible defects on both the outer and inner surfaces, and even when the cross section is polished and observed under a microscope, no voids or delamination are found, indicating excellent properties. It was Since both ends of the core that were in contact with the air were burnt black, both ends were cut off to regenerate the core.

Example 2 The same procedure as in Example 1 was carried out except that a core of an ultra-high molecular weight polyethylene was used as a core and a heat-shrinkable tube made of Teflon was closely adhered to the core to cover the surface. The quality of the obtained pipe was the same as in Example 1, and the both ends of the used core were not burnt black and were re-exposed in the oven.
By heating at 280 ° C and then slowly cooling, the core could be returned to a reusable state.

Comparative Example 1 The procedure of Example 1 was repeated, except that the core material was PTFE. At 280 ℃, the thermal expansion of PTFE was lower than that of ultra-high molecular weight polyethylene, so the embossing was insufficient, and voids were still left between the layers in the obtained pipe. Comparative Example 2 A pipe was molded in the same manner as in Comparative Example 1, and a 21 mmφ PTFE core was inserted into the pipe again, followed by heating at 280 ° C. for 1 hour and subsequent cooling.

The pipe molded in this manner has no externally visible defects on both the outer surface and the inner surface, and even when the cross section is polished and observed under a microscope, voids and delamination are not found, which is an excellent property. Was shown. However, the quality of the resulting pipe was similar to that of Example 1, but the molding required two heating / cooling steps.

[0022]

As described above, according to the present invention, since a heat-expandable core made of ultra-high molecular weight polyethylene is used, a matrix resin of a thermoplastic resin having a softening point or melting point of 160 ° C to 300 ° C is used. It is possible to efficiently manufacture a fiber-reinforced thermoplastic resin pipe from the prepreg.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between temperature and thermal expansion of ultra high molecular weight polyethylene.

FIG. 2 is a perspective explanatory view showing a cylindrical outer die.

FIG. 3 is a perspective explanatory view showing a positional relationship among a cylindrical outer die, a preform and a core.

FIG. 4 is an explanatory perspective view showing an example of a fiber reinforced thermoplastic resin pipe.

[Explanation of symbols]

1 cylindrical outer mold, 2 preform, 3 core,
4 pipes.

Claims (3)

[Claims] 1. A prepreg containing a thermoplastic resin having a softening point or a melting point of 160 ° C. to 300 ° C. as a matrix and containing reinforcing fibers on a heat-expandable core made of ultra-high molecular weight polyethylene and on the outside of the core. The core and the prepreg are then cooled by cooling the core and the prepreg by interposing them between the outer mold and the outer mold, and then heating the prepreg and the core to soften or melt the thermoplastic resin and expand the core. A method for producing a fiber-reinforced thermoplastic resin pipe comprising: 2. The method for producing a fiber-reinforced thermoplastic resin pipe according to claim 1, wherein the heat-expandable core is an ultrahigh molecular weight polyethylene mandrel. 3. The method for producing a fiber-reinforced thermoplastic resin pipe according to claim 1, wherein the heat-expandable core is a mandrel of ultra-high molecular weight polyethylene having a fluororesin layer provided on the surface thereof.